JP2007244121A - Partial resonance switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a partial resonance switching power supply which activates timing for starting turnon of a switching element at a point of a bottom voltage of a partial resonance waveform or a half period of the partial resonance, and reduces a switching loss and a switching noise regardless of a high-frequency drive signal. <P>SOLUTION: The partial resonance switching power supply is provided with the switching control means 2 for detecting a primary input voltage V1 and an output current Io, calculating an oscillation frequency f and a duty D ä=TON/(TON+TOFF)} for driving a MOSFET-Q1, calculating an OFF duration TOFF from the duty D ä=TON/(TON+TOFF)} and the oscillation frequency f, generating a switch-on signal SON at a timing when an addition äTOFF+π√(LK×CDS)} of the calculated OFF duration TOFF and the half period ä=π√(LK×CDS)} (= a delay time Tr) of the partial resonance previously stored are obtained, and driving the MOSFET-Q1 using the switch-on signal SON. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a partial resonance type switching power source that reduces switching loss by driving a switching element to ON (bottom ON) at a bottom potential point of a partial resonance waveform.

  In conventional switching power supplies, when a switching element is driven to turn on, a high voltage is often applied between the switching elements (off state). Especially in a case where the driving frequency is high, the switching element is turned on. In the process, since a current flows through the switching element in a state where there is a voltage between the switching elements, a switching loss occurs, resulting in a decrease in the efficiency of the entire power supply.

  FIG. 9 shows a voltage waveform, a current waveform, and a switching loss waveform diagram of a conventional switching power supply. For example, the case where a MOSFET is used as a switching element is shown. During the MOSFET OFF period TOFF, the drain-source voltage VDS of the MOSFET is high, and when it is turned on, The MOSFET drain-source voltage VDS shifts to a sufficiently low on state.

  Since the current IDS flows when the drain-source voltage VDS between the MOSFETs is sufficiently lowered from the high voltage, a switching loss Ps (= VDS × IDS), which is the product of the voltage VDS and the current IDS, occurs.

  Accordingly, it is desirable that the voltage between the switching elements (for example, the drain-source voltage VDS) is sufficiently low at the moment when the switching element is turned on from off.

  A partial resonance type switching power supply is used for the purpose of sufficiently reducing the voltage between the switching elements at the moment when the switching elements are turned on from off.

  The partial resonance type switching power supply uses, for example, a partial resonance that occurs in a state in which the switching element is turned on from an off state by using a leakage inductance of an insulating transformer used for the switching power supply and a capacitance between the switching elements. In the OFF state, the switching element is turned on at the timing when the voltage between the switching elements decreases.

A conventional partial resonance type switching power supply is, for example, disclosed in “Patent Document 1” (switching power supply device) with an oscillation operation combining a soft drive and partial resonance with respect to a small load in a standby mode, thereby improving the efficiency of the power supply. It has been disclosed to reduce noise.
JP 2002-315333 A (see abstract)

  The conventional partial resonance type switching power supply disclosed in “Patent Document 1” describes that a switching element is driven by a soft drive and a resonance operation at a frequency synchronized with a power supply frequency with respect to a minute load, and is substantially zero volt switching. Has been.

  However, when the switching element is driven at a high frequency (for example, 50 Kz or 100 Kz), switching loss and switching noise may increase unless the on-timing of the switching element is set to the resonance frequency of zero volts. Because it is not, it is unknown.

  The present invention has been made to solve such a problem, and the object thereof is to execute the on-timing timing of the switching element at the point of the bottom voltage of the partial resonance waveform or the half cycle of the partial resonance. Another object of the present invention is to provide a partial resonance type switching power supply that reduces switching loss and switching noise even with high-frequency driving signals.

  In order to solve the above-mentioned problems, a partial resonance type switching power supply according to the present invention is a partial resonance type switching power supply that optimizes the on-start of a switching element of a DC-DC converter using partial resonance and reduces switching loss. The switching control means for driving the start of the switching element at the timing when the partial resonance waveform becomes the bottom voltage (bottom ON) is provided.

  The partial resonance type switching power supply according to the present invention includes the switching control means for driving the switching element on start at the timing when the partial resonance waveform becomes the bottom voltage (bottom ON). Starting from a low voltage portion, switching loss and switching noise when the switching element is turned on can be reduced.

  Further, the switching control means according to the present invention detects the primary side input voltage and the secondary side output current, calculates the OFF period (TOFF) of the switching element from the primary side input voltage and the secondary side output current, The switching element is turned on at the bottom (TOFF + TD) by calculating the 1/2 period (TD) of the resonance waveform and adding the delay time (Tr) of the 1/2 period (TD) to the OFF period (TOFF). Features.

  The switching control means according to the present invention detects a primary-side input voltage and a secondary-side output current, calculates an OFF period (TOFF) of the switching element from the primary-side input voltage and the secondary-side output current, and has a partial resonance waveform. The switching element is turned on at the bottom (TOFF + TD) at the timing (TOFF + TD) obtained by calculating the 1/2 period (TD) of the signal and adding the delay time (Tr) of the 1/2 period (TD) to the OFF period (TOFF). And the time until the bottom voltage of the partial resonance that occurs following the off period (delay time Tr) is calculated, and the switching element is turned on. ), The switching loss and switching noise when the switching element is turned on. It is possible to reduce the figure.

  Further, the switching control means according to the present invention detects a primary side input voltage and a secondary side output voltage, and calculates a bottom voltage (VBO) of the partial resonance waveform from the primary side input voltage and the secondary side output voltage. It memorizes, detects the voltage (VDS) between the switching elements, and bottoms the switching element at the timing when the bottom voltage (VBO) becomes equal to the voltage (VDS) between the switching elements (VBO = VDS). And

  The switching control means according to the present invention detects a primary side input voltage and a secondary side output voltage, calculates and stores a bottom voltage (VBO) of a partial resonance waveform from the primary side input voltage and the secondary side output voltage, Since the voltage (VDS) between the switching elements is detected and the bottom voltage (VBO) becomes equal to the voltage (VDS) between the switching elements (VBO = VDS), the switching element is turned on at the bottom, so the partial resonance waveform is The turn-on of the switching element can be started at a timing when the voltage (VDS) between the switching elements at the time of decrease coincides with the stored bottom voltage (VBO).

  Further, the switching control means according to the present invention detects and stores the OFF voltage value during the OFF period (TOFF) between the switching elements, and the OFF voltage value decreases due to the start of partial resonance, and shifts to partial resonance. The switching element is bottom-ON at the timing of the delay time (Tr) of ½ period (TD) of the partial resonance waveform from the moment when the instantaneous resonance voltage value is detected.

  The switching control means according to the present invention detects and stores the OFF voltage value of the OFF period (TOFF) between the switching elements, and the OFF voltage value decreases at the start of partial resonance, and at the moment when the transition to partial resonance occurs. Since the switching element is bottom-ON at the timing of the delay time (Tr) of 1/2 period (TD) of the partial resonance waveform from the time when the resonance voltage value is detected, the part from the end of the OFF period (TOFF) between the switching elements When the resonance starts, the switching element can be turned on with a delay time (Tr) delayed by a half period of the partial resonance.

  Furthermore, the switching control means according to the present invention detects the OFF period (TOFF) from the drive signal for driving the switching element, and the delay time (Tr) of the half period (TD) of the partial resonance waveform from the OFF period. The switching element is bottom-ON at timing.

  The switching control means according to the present invention detects the OFF period (TOFF) from the drive signal for driving the switching element, and at the timing of the delay time (Tr) of ½ period (TD) of the partial resonance waveform from the OFF period, Since the switching element is turned on at the bottom, the driving signal inside the control means is monitored, and the switching element is turned on at an optimum point only by adding to the driving signal a delay time (Tr) delayed by a half period of partial resonance. be able to.

  The partial resonance type switching power supply according to the present invention includes the switching control means for driving the switching element on start at the timing when the partial resonance waveform becomes the bottom voltage (bottom ON). Starting from a low voltage portion, the switching loss and switching noise when the switching element is turned on can be reduced, and the overall efficiency of the power supply can be improved.

  Further, the switching control means according to the present invention detects the primary side input voltage and the secondary side output current, calculates the OFF period (TOFF) of the switching element from the primary side input voltage and the secondary side output current, The switching element is turned on at the bottom (TOFF + TD) at the timing (TOFF + TD) obtained by calculating the 1/2 period (TD) of the resonance waveform and adding the delay period (Tr) of the 1/2 period (TD) to the OFF period (TOFF). The switching element OFF period and the time until the bottom voltage of the partial resonance that occurs following the OFF period (delay time Tr) are calculated, and the switching element is turned on from the switching element OFF period so that the partial resonance waveform has a minimum voltage ( Starting from the timing of the delay time (Tr) that becomes the bottom voltage), the switching loss and the switch when the switching element is turned on Can be reduced Gunoizu, it can be turned on Suitchigu element at an optimum timing.

  Further, the switching control means according to the present invention detects the primary side input voltage and the secondary side output voltage, calculates the bottom voltage (VBO) of the partial resonance waveform from the primary side input voltage and the secondary side output voltage, and stores it. Since the voltage between the switching elements (VDS) is detected and the bottom voltage (VBO) becomes equal to the voltage between the switching elements (VDS) (VBO = VDS), the switching element is turned on at the bottom, so partial resonance The switching element can be turned on at a timing when the voltage between the switching elements (VDS) when the waveform is reduced matches the stored bottom voltage (VBO), and the switching loss and switching when the switching element is turned on Noise can be reduced.

  Further, the switching control means according to the present invention detects and stores the OFF voltage value during the OFF period (TOFF) between the switching elements, and the OFF voltage value decreases due to the start of partial resonance, and shifts to partial resonance. Since the switching element is turned on at the bottom of the delay time (Tr) of the half period (TD) of the partial resonance waveform from the moment when the instantaneous resonance voltage value is detected, the OFF period (TOFF) between the switching elements ends. When the partial resonance starts, the switching element can be turned on with a delay time (Tr) delayed by a half cycle of the partial resonance. By simply monitoring the voltage value of the partial resonance waveform, the switching element can be switched at an optimum timing. Can be turned on.

  Furthermore, the switching control means according to the present invention detects the OFF period (TOFF) from the drive signal for driving the switching element, and the delay time (Tr) of the half period (TD) of the partial resonance waveform from the OFF period. At the timing, the switching element is turned on at the bottom. The drive signal inside the control means is monitored, and the switching element is turned on by simply adding the delay time (Tr) delayed by a half period of partial resonance to the drive signal. It is possible to implement this method, and it is possible to appeal the simplification of the system and the reduction of switching loss and switching noise when the switching element is turned on.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a first embodiment of a partial resonance type switching power supply according to the present invention. In FIG. 1, a partial resonance type switching power supply 1 includes a diode bridge DB for full-wave rectification of an AC power supply VAC (100 V / 200 V, 50 Hz / 60 Hz, etc.) and a smoothing capacitor for smoothing the full-wave rectified primary side input voltage V1. C1, an isolation transformer T, and a MOSFET-Q1 that is connected in series to the primary winding Np of the isolation transformer T and that constitutes a switching element that generates a high-frequency signal (for example, 50 Kz) by switching the smoothed voltage. , A secondary power supply NS of the isolation transformer T, a rectifier diode D1 and a smoothing capacitor C2, a main power supply circuit for generating a secondary output voltage (DC) Vo, and switching for controlling the on / off operation of the MOSFET-Q1 It comprises a control means 2 and an output current detection (means) 3 for detecting an output current Io flowing through the load L. There.

  The partial resonance type switching power supply 1 is formed with a leakage inductance Lk generated in the isolation transformer T and a parasitic capacitance generated between the drain and source of the MOSFET-Q1 or an electrostatic capacitance connected between the drain and source. Due to the drain-source capacitance CDS, partial resonance is generated at the end of the OFF period TOFF of the MOSFET-Q1.

  The switching control means 2 is basically composed of a microprocessor and includes a drive signal generation function, a calculation function, a timer function, a primary side input voltage detection function, an output current detection function, a drive signal output function, and the like.

  The switching control means 2 detects the input voltage information J1 obtained by resistance-dividing the primary side input voltage V1 with the resistors R1 and R2 and the output current Io flowing through the current detection resistor Rx with the output current detection (means) 3. The supplied output current information JI is taken, the duty D {= TON / (TON + TOFF)} and the oscillation frequency f for driving the MOSFET-Q1 are calculated based on the input voltage information J1 and the output current information JI, and the duty D { = TON / (TON + TOFF)} and the oscillation frequency f are stored.

  Further, the switching control means 2 calculates an OFF period TOFF from the calculated duty D {= TON / (TON + TOFF)} and the oscillation frequency f.

  Further, the switching control means 2 calculates the half period of the partial resonance {= π√ (LK × CDS) previously calculated and stored from the leakage inductance Lk and the drain-source capacitance CDS during the calculated OFF period TOFF. } (= Delay time Tr) is added {TOFF + π√ (LK × CDS)}, 1/2 cycle {π√ (LK × CDS)} is monitored from the start point of the OFF period TOFF, and 1/2 cycle {π A switch-on signal SON is generated at the timing of the end of √ (LK × CDS)}, and the MOSFET-Q1 is driven to be turned on by the switch-on signal SON.

  FIG. 2 is a voltage waveform and current waveform control diagram of the first embodiment of the switching control means according to the present invention. In FIG. 2, the voltage waveform (drain-source voltage VDS) indicates that the switching control means 2 ends the half period {= π√ (LK × CDS)} of the partial resonance from the start of the OFF period TOFF of the drive signal SD. At this time, the switch-on signal SON is output and the MOSFET-Q1 is turned on, so that the MOSFET-Q1 can be turned on at the lowest voltage level (bottom voltage Vbo) of the partial resonance waveform WB. Switching loss and switching noise associated with turning on can be reduced.

  The current waveform (drain-source current IDS) starts to flow from the point of turn-on, and the switching loss Ps, which is the product of the drain-source current IDS and the drain-source voltage VDS (= IDS × VDS), is also kept very low. Can do.

  As described above, the switching control means 2 according to the present invention detects the primary side input voltage V1 and the secondary side output current (output current Io), and from the primary side input voltage V1 and the output current Io, the switching element (MOSFET-Q1). ), The half period TD of the partial resonance waveform is calculated, and the switching element (MOSFET−) is calculated at the timing (TOFF + TD) obtained by adding the delay period Tr of the 1/2 period TD to the OFF period TOFF. Since Q1) is bottom-ON, the switching element OFF period TOFF and the time from the partial resonance bottom voltage generated following the OFF period TOFF {π√ (LK × CDS)} = (delay time Tr)} are calculated. The turn-on of the switching element is delayed from the switching element OFF period until the partial resonance waveform becomes the minimum voltage (bottom voltage Vbo) ( Was started at the timing of r), the switching loss at the turn-on time of the switching elements and can reduce switching noise, it is possible to turn on the Suitchigu element at an optimum timing.

  FIG. 3 is an overall configuration diagram of a second embodiment of a partial resonance type switching power supply according to the present invention. In FIG. 3, the partial resonance type switching power supply 4 is provided with a switching control means 5, an output voltage detection (means) 6, and resistors R3 and R4 for dividing and detecting the drain-source voltage VDS. 1 is different from the partial resonance type switching power supply 1 shown in FIG.

  The switching control means 5 is basically composed of a microprocessor, and includes a drive signal generation function, a calculation function, a timer function, a comparison function, a primary side input voltage detection function, an output voltage detection function, a drive signal output function, and the like.

  The switching control means 5 is supplied by detecting the input voltage information J1 obtained by dividing the primary side input voltage V1 by resistors R1 and R2 and the secondary side output voltage (DC) Vo by the output voltage detection (means) 6. Output voltage information jo and drain-source voltage VDS obtained by resistance-dividing the drain-source voltage VDS with resistors R3 and R4, and the bottom voltage Vbo (√2) based on the input voltage information J1 and the output voltage information jo (* V1-Np * Vo / Ns) is calculated and stored.

  Further, the switching control means 5 monitors the drain-source voltage information JDS, and when the partial resonance occurs after the OFF period TOFF of the drain-source voltage VDS ends, the drain-source voltage of the partial resonance waveform WB. VDS is compared with the stored resonance bottom voltage Vbo, and when the drain-source voltage VDS becomes equal to the bottom voltage Vbo (VDS = Vbo), the switch-on signal SON is output to turn on MOSFET-Q1 ( Bottom ON) Drives.

  Since the bottom voltage Vbo is the minimum voltage level of the partial resonance waveform WB, the MOSFET-Q1 can be turned on with the drain-source voltage VDS being small even when the MOSFET-Q1 is in the off state.

  FIG. 4 is a voltage waveform and current waveform control diagram of the second embodiment of the switching control means according to the present invention. In FIG. 4, the voltage waveform (drain-source voltage VDS) shows that the drain-source voltage VDSX of the partial resonance waveform WB coincides with the bottom voltage Vbo from the final point of the OFF period TOFF of the drive signal SD by the switching control means 5. At the time (VDSX = Vbo), the switch-on signal SON is output and the MOSFET-Q1 is turned on (turned on), so that the MOSFET-Q1 can be turned on at the lowest voltage level (bottom voltage Vbo) of the partial resonance waveform WB. In addition, switching loss and switching noise associated with turning on of the MOSFET-Q1 can be reduced.

  The current waveform (drain-source current IDS) starts to flow from the point of turn-on, and the switching loss Ps, which is the product of the drain-source current IDS and the drain-source voltage VDS (= IDS × VDS), is also kept very low. Can do.

  As described above, the switching control means 5 according to the present invention detects the primary side input voltage V1 and the secondary side output voltage (secondary side output voltage (DC) Vo), and detects the primary side input voltage and the secondary side output voltage. Is used to calculate and store the bottom voltage (VBO) of the partial resonance waveform WB, detect the voltage (VDS) between the switching elements (MOSFET-Q1), and the bottom voltage (VBO) is the voltage between the switching elements (VDSX). Since the switching element is bottom-ON at the timing equal to (VBO = VDSX), the voltage (VDSX) between the switching elements when the partial resonance waveform decreases coincides with the stored bottom voltage (VBO), The switching element can be turned on, and switching loss and switching noise when the switching element is turned on can be reduced. Kill.

  FIG. 5 is an overall configuration diagram of a third embodiment of a partial resonance type switching power supply according to the present invention. In FIG. 5, the partial resonance type switching power supply 7 includes the switching control means 8 and resistors R3 and R4 that divide and detect the drain-source voltage VDS. The partial resonance type switching power supply 1 shown in FIG. And different.

  The switching control means 8 is basically constructed of a microprocessor and has a drive signal generation function, a calculation function, a timer function, a storage function, and a drive signal output function.

  The switching control means 8 detects and stores the OFF voltage value (drain-source voltage VDS) during the OFF period of the MOSFET-Q1 from the drain-source voltage information JDS, and stores the OFF voltage value (drain-source voltage VDS). Decreases from the start of partial resonance, and when the resonance voltage value (drain-source voltage V DSK) at the moment of transition to partial resonance is detected, ½ period (TD = {π√ (LK) of the partial resonance waveform WB The switch-on signal SON is output at the timing of the delay time Tr of (CDS)}), and the MOSFET-Q1 is turned on (turned on).

  FIG. 6 is a voltage waveform and current waveform control diagram of the third embodiment of the switching control means according to the present invention. In FIG. 6, the voltage waveform (drain-source voltage VDS) indicates that the switching control means 8 stores the drain-source voltage VDS which is the off-voltage during the OFF period TOFF of the drive signal SD, and the partial resonance is started. From the time when the drain-source voltage VDSK of the resonance waveform WB is slightly lower than the drain-source voltage VDS which is the off voltage, the half period (TD = {π√ (LK × CDS)} of the partial resonance waveform WB ) To generate the switch-on signal SON at the timing of the delay time Tr, so that the MOSFET-Q1 can be turned on, and the MOSFET-Q1 can be controlled at the optimum timing by simply monitoring the resonance start voltage VDSK of the partial resonance waveform WB. It can be driven on (turn on).

  The current waveform (drain-source current IDS) starts to flow from the point of turn-on, and the switching loss Ps, which is the product of the drain-source current IDS and the drain-source voltage VDS (= IDS × VDS), is also kept very low. Can do.

  Thus, the switching control means 8 according to the present invention detects and stores the OFF voltage value (drain-source voltage VDS) in the OFF period (TOFF) between the MOSFET and Q1, and stores the OFF voltage value (VDS). ) Decreases due to the start of partial resonance, and when the resonance voltage value (resonance start voltage V DSK) at the moment of transition to partial resonance is detected, ½ period (TD = {π√ (LK × Since the bottom of the MOSFET-Q1 is turned ON at the timing of the delay time (Tr) of (CDS)}), when the partial resonance starts from the end of the OFF period (TOFF) between the MOSFET and Q1, the delay time delayed by a half cycle of the partial resonance. At (Tr), the turn-on of the MOSFET-Q1 can be started, and the MOSFET-Q1 can be turned on at an optimum timing only by monitoring the voltage value of the partial resonance waveform. Kill.

  FIG. 7 is a block diagram showing an embodiment of the switching control means according to the present invention. In FIG. 7, the switching control means 9 is basically composed of a microprocessor and has a drive signal generating function, a drive signal monitoring function, a timer function, and a drive signal output function.

  The switching control means 9 detects the OFF period TOFF from the switch-off signal SOFF when the drive signal SD (repeat of the switch-on signal SON and the switch-off signal SOFF) is output, and from the OFF period TOFF, 1 / of the partial resonance waveform WB. At the timing of the delay time Tr of two periods (TD = {π√ (LK × CDS)}), the switch-on signal SON that turns on the MOSFET-Q1 is output.

  Since the switch-on signal SON is provided to the MOSFET-Q1 from the OFF period TOFF of the switch-off signal SOFF with the delay time Tr of the half period TD of the partial resonance waveform WB, the MOSFET-Q1 is supplied with the bottom voltage Vbo of the partial resonance waveform WB. It can be turned ON.

  FIG. 8 is a voltage waveform, current waveform and switching loss waveform control diagram of the fourth embodiment of the switching control means according to the present invention. In FIG. 8, the voltage waveform (drain-source voltage VDS) is stored in the switching control means 9 by monitoring and storing the OFF period TOFF of the drive signal SD, and following the OFF period TOFF, 1 of the partial resonance waveform WB. / 2 period (TD = {π√ (LK × CDS)}) is applied to generate a switch-on signal SON at a timing to which the delay time Tr is applied, and the MOSFET-Q1 can be turned on. Only by processing, the turn-on of the MOSFET-Q1 can be executed at an optimum point.

  The current waveform (drain-source current IDS) starts to flow from the point of turn-on, and the switching loss Ps, which is the product of the drain-source current IDS and the drain-source voltage VDS (= IDS × VDS), is also kept very low. Can do.

  Thus, the switching control means 9 according to the present invention detects the OFF period (TOFF) from the drive signal SD for driving the MOSFET-Q1, and from the OFF period, ½ period (TD = { Since the MOSFET-Q1 is bottom-ON at the timing of the delay time (Tr) of π√ (LK × CDS)}), the drive signal SD inside the control means is monitored, and the delay time Tr delayed by a half cycle of the partial resonance is obtained. It is possible to execute the turn-on of the MOSFET-Q1 at an optimum point only by giving it to the drive signal SD, and to appeal the simplification of the method and the reduction of the switching loss Ps and the switching noise when the MOSFET-Q1 is turned on. Can do.

  In the present embodiment, the switching element is configured by a MOSFET, but may be configured by an IGBT (insulated gate transistor).

  Further, the switching control means is constituted by a microprocessor, but may be constituted by a DSP (Digital Signal Processor).

  As described above, the partial resonance type switching power supplies 1, 4 and 7 according to the present invention drive the start of turning on of the switching element (MOSFET-Q 1) at the timing when the partial resonance waveform WB becomes the bottom voltage Vbo (bottom ON). Switching control means 2, 5, 8, and 9, so that the switching element (MOSFET-Q 1) starts to be turned on at a low part of the switching element voltage (drain-source voltage VDS). It is possible to reduce the switching loss Ps and the switching noise at the turn-on time of -Q1), and to improve the overall efficiency of the power supply.

  The partial resonance type switching power supply according to the present invention starts the switching element from the part where the voltage between the switching elements is low, aiming at the half period of the partial resonance waveform or the bottom voltage Vbo, and turns on the switching element. Switching loss and switching noise at the time can be reduced, and can be applied to any partial resonance type switching power supply.

Overall configuration diagram of a first embodiment of a partial resonance type switching power supply according to the present invention First embodiment of switching control means according to the present invention Voltage waveform and current waveform control diagram Overall configuration diagram of a second embodiment of a partial resonance type switching power supply according to the present invention Second Embodiment of Switching Control Unit According to the Invention Voltage waveform and current waveform control diagram Overall configuration diagram of third embodiment of partial resonance type switching power supply according to this invention Third Embodiment of Switching Control Unit According to the Invention Voltage waveform and current waveform control diagram Block diagram of an embodiment of switching control means according to the present invention Fourth Embodiment of Switching Control Unit According to the Invention Voltage waveform, current waveform and switching loss waveform control diagram Voltage waveform, current waveform and switching loss waveform diagram of conventional switching power supply

Explanation of symbols

1, 4, 7 Partially resonant switching power supply 2, 5, 8, 9 Switching control means 3 Output voltage detection (means)
6 Output current detection (means)
DB diode bridge D1 rectifier diode C1, C2 smoothing capacitor T isolation transformer Np primary winding Ns secondary winding Q1 MOSFET
R1, R2, R3, R4 Resistor Rx Current detection resistor Lk Leakage inductance CDS Drain-source capacitance V1 Primary side input voltage Vo Secondary side output voltage (DC)
VDS drain-source voltage VDSX resonance voltage VDSK resonance start voltage Vbo bottom voltage Io output current J1 input voltage information jo output voltage information JDS drain-source voltage information JI output current information SD drive signal SON switch-on signal IDS drain-source current TOFF OFF period WB Partial resonance waveform TD Partial resonance half period Tr Delay time Ps Switching loss VAC AC power supply L Load

Claims (5)

A partial resonance type switching power supply that optimizes the on-start of a switching element of a DC-DC converter using partial resonance and reduces switching loss,
A partial resonance type switching power supply comprising switching control means for driving the on-start of the switching element at a timing when the partial resonance waveform becomes a bottom voltage (bottom ON). The switching control means detects a primary side input voltage and a secondary side output current, calculates an OFF period (TOFF) of the switching element from the primary side input voltage and the secondary side output current, and A half cycle (TD) is calculated, and the switching element is bottom-ON at a timing (TOFF + TD) obtained by adding the delay time (Tr) of the 1/2 cycle (TD) to the OFF period (TOFF). The partial resonance type switching power supply according to claim 1, wherein: The switching control unit detects a primary side input voltage and a secondary side output voltage, calculates and stores a bottom voltage (VBO) of the partial resonance waveform from the primary side input voltage and the secondary side output voltage, and stores the switching The voltage between the elements (VDS) is detected, and the bottom of the switching element is turned on at the timing when the bottom voltage (VBO) becomes equal to the voltage between the switching elements (VDS) (VBO = VDS). The partial resonance type switching power supply according to claim 1. The switching control means detects and stores an OFF voltage value during an OFF period (TOFF) between the switching elements, and the resonance at the moment when the OFF voltage value decreases due to the start of partial resonance and shifts to the partial resonance. 2. The partial resonance type according to claim 1, wherein the switching element is bottom-ON at a timing of a delay time (Tr) of a half period (TD) of the partial resonance waveform from the time when the voltage value is detected. Switching power supply. The switching control means detects an OFF period (TOFF) from a drive signal for driving the switching element, and at a timing of a delay time (Tr) of ½ period (TD) of the partial resonance waveform from the OFF period, 2. The partial resonance type switching power supply according to claim 1, wherein the switching element is bottom-ON.

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